Description

As of r9297, which django.contrib.admin.helpers now utilizes formset.fk, generic inline formsets now break attempting to access formset.fk. Attached is a simple fix, though I suspect there's more work to be done with generic and r9297.

Are indeed _not_ useless! It's absolutly clear (now - for me - finally), that
we of course don't need the ForeignKey in a GenericInlineFormSet, because it's
clear that we set the ForeignKey according the Model we are "inlining". So without
the "else" from the snippet, I always had a content_type and object_id field in
my inline-form, what seems to be a new-self-produced-bug - means: re-add those two
lines and restart searching, why I always get: ​http://nopaste.com/p/aJeKlSyvj

The problem with this is, the fk_field is beeing called directly from the template,
so there is no way to avoid beeing asked for the fk_field-widget. As mentioned before,
we have absolutly no need for the fk-field, as it gets set automaticly by the parent
model. So i just looked for the output-method for fk_field - in contrib/admin/helpers.py: